Project Abstract The current supplement is submitted in response to PA-18-591, ?Administrative Supplements to Existing NIH Grants and Cooperative Agreements.? Our parent grant is #R24ODO21606 (Jan Nolta, Joseph Anderson Co-PIs): Novel Immune Deficient mouse Models of Huntington's disease for Human Stem Cells 4/1/17-12/30/20. This special interest opportunity is of particular importance to the outcome of our R24 grant, due to the ability to establish dedicated personnel and equipment to assess the efficacy of our Humanized Immune System (HIS) mouse models. Due to the increase in animals needed to complete the R24 and ?HIS supplement to assess mPB? updating the capability of existing equipment in the Nolta lab is needed to help facilitate the successful completion of this project. The goal of the supplement is to purchase additional upgrades (two additional lasers and detectors as well as an autosampler plate loader to increase automation) for the Attune Flow Cytometer in the Nolta lab to increase capabilities. This administrative supplement is of particular importance to the outcome of our R24 grant, due to the need to perform complete characterization of engrafted human cells in healthy wild-type mice to assess optimized donor conditions and in transgenic neurodegenerative models to assess the impact of disease-state on immune cells.